When Lance Shaw, an amateur astronomer from Pinole, looks back over 1999, he remembers that his most spine-tingling moment occurred in the wee hours of February 25.

He was about to witness something extraordinarily rare, something that only one other person had seen since 1987, and then only hours previously: a nearly invisible star suddenly becoming brilliant, a star that didn't belong there.

"I had gotten an alert notice over the Internet from a guy in Germany," said Shaw, 35, whose day job is as a technician at the Tosco refinery near Martinez. "He said the star U Scorpii was in outburst for the first time since 1987."

It was pouring rain when Shaw received the alert at 3:30 a.m. Then, with uncanny timing, the sky cleared 45 minutes before sunrise, and Shaw was able to confirm the outburst with a pair of binoculars, standing in his bathrobe.

"It was the perfect moment. I knew where to look. I shot off a quick e-mail on the Web. It was like, let's crank it up (point your telescopes), guys, it's there!"

The number of sky-gazing devotees has grown substantially in recent years, thanks in part to excitement over the discoveries of the comets Hyakutake and Hale-Bopp, the Galileo spacecraft now surveying Jupiter and its moons, and spectacular images from the Hubble space telescope.

More importantly, amateur astronomers are being taken far more seriously by their professional counterparts, who rely on them more frequently to track variable stars, like U Scorpii, or collect data on meteors, which scientists at NASA Ames in Mountain View are particularly interested in.

"With the Internet, we are in kind of a golden age of amateur astronomy," said Mike Koop, an electrical engineer for Lockheed Martin and a member of the San Jose Astronomical Association. "We can link together and get the word out instantly."

Amateurs themselves are beginning to make major discoveries, thanks in part to more sophisticated equipment.

The Hale-Bopp comet, for example, was co-discovered July 22, 1995, by amateur comet hunter Thomas Bopp of Glendale, Ariz., and professional astronomer Alan Hale of Cloudcroft, N.M., who independently found a tiny, fuzzy spot in the sky where catalogs list no star. Bopp was using a friend's homemade 17 1/2-inch reflector telescope.

The comet Hyakutake was spotted Jan. 30, 1995, by Japanese photoengraver and amateur astronomer Yuji Hyakutake, using special large binoculars. It was 166 million miles from the sun, or a bit farther out than Mars.

Astronomy happens to be one of the few sciences in which amateurs can make real contributions to research, said Seth Shostak, an astronomer with the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View.

"Astronomy is, above all, an observing science," said Shostak, who regularly heads down to Arecibo, Puerto Rico, to monitor radio signals from stars in the hope of hearing an intelligent signal. "The tools professional astronomers use tend to look at very tiny slivers of the sky. The Hubble telescope is like holding a pinhole at arm's length. The amateurs with their binoculars and small telescopes may use far less sensitive equipment than we do, but they are looking at the whole sky."

In November, six Bay Area amateur astronomers accompanied scientists from the National Aeronautics and Space Administration on a meteor hunt during the Leonid storm. They rode alongside astronomers in two U.S. Air Force Boeing 707s using advanced equipment -- and some not so advanced -- to plot things like magnitude, orbits and velocities of meteors. The trip took them over England to Israel and the Azores during the course of four nights.

Equipped with special goggles that intensified the light from the meteors, video cameras and military electronics, the amateurs together were able to count up to 15,000 meteors in one night over the Azores. They observed meteors streaking through the aurora borealis, and they saw "sprites," upward lightning strikes thought to be induced by meteors.

"These dedicated people are absolutely essential to our work because there is not enough funding to employ enough people and train them," said Peter Jenniskens, a NASA Ames astronomer and principal organizer of the amateur astronomers for the Leonid project. "I am actually helping some amateur astronomers publish results. Amateurs can collect data, but to interpret it you need an astronomer, so these people really help us keep programs going."

NASA is eager for this kind of data to better predict when meteor showers and storms are going to occur, because meteors can damage satellites, said Jane Houston, 47, an astronomer from San Rafael who was one of the six amateurs aboard Jenniskens' Leonid project. Her day job is as an information technology consultant.

"Both NASA and the Air Force, which paid for the project, were very interested in finding out what these meteors were made of, what organic materials came to Earth through meteors," said Houston, who is president of the Astronomical Association of Northern California.

"We amateurs have our own equipment, and we can observe 365 nights a year if we so choose and we enjoy doing it. We are sort of like free labor for the professionals."

For Houston, part of the excitement of amateur astronomy is the sense that she is contributing something vitally important to the scientific community. But it's also social.

"You get to work with other people with similar interests, and while we look at pretty galaxies and make sketches of what we see, we get to know one another very well. It's a great hobby for women -- most of the amateurs are men. It can get very romantic on top of peaks at night."

Indeed. Houston met her future husband, fellow amateur astronomer Morris Jones, one starry night on Fremont Peak in the South Bay. They got married this past weekend and plan to honeymoon in the Blue Mountains, 200 miles east of Sydney, Australia, where hundreds of amateur astronomers will gather to gaze at the heavens.

RESOURCES

Here is a sampling of amateur astronomy groups in Northern California. Most of the larger clubs have monthly newsletters, indoor lectures and outdoor star parties, weather permitting.

-- Astronomical Association of Northern California (www.aanc-astronomy.org) -- Web site includes a comprehensive list of clubs from Chico to Santa Cruz.

-- Sonoma County Astronomical Society -- Offers a Young Astronomers section and a telescope-building program. For information, write P.O. Box 183, Santa Rosa, CA 95402, or e-mail club president at blbaron@worldnet.att.net.